JFK was very strong on defense -as well as initiated pre-emptive operations in Vietnam, and was successful in across-the-board tax cuts that spurred a period of strong economic growth. JFK's supply-side initiative cut short the economic stagnation that was creeping in and ushered in a new era of economic pro-business prosperity.
LBJ then took the increased revenues and greatly expanded the role of government, utilizing the then-dead JFK "legacy" as the means of getting it done. With the cost of war, and the ever increasing size and scope of his "Great Society" government makeover, the increased revenues of created by the JFK tax cuts were soon gone - and the economic flatline that took place in the 1970s was soon to follow.
Watch this video of JFK and it becomes clear that the Democrat Party of then, bears very little resemblance to the Democrat Party of today. JFK was a supply-sider, a social issues moderate, and international hawk.
http://www.youtube.com/watch?v=aEdXrfIMdiU